As the natural pressure in a completed oil well gradually depletes, the well may require a means known as artificial lift to continue the flow of petroleum reserves from their subterranean location to the earth's surface. Various forms of artificial lift are known including, for example, gas injection, water injection, and mechanical pumping. Petroleum engineers select a form of artificial lift depending on a number of criteria including, for example, formation geology and economics. The sucker rod pump is a well-known kind of mechanical pump that is widely used in the petroleum industry.
The sucker rod pumping system typically includes a means of providing a reciprocating (up and down) mechanical motion located at the surface near the well head. A string of sucker rods—up to more than a mile in length—is connected to the mechanical means. The sucker rod string is fed through the well tubing down hole where it is connected to the pump.
As is generally known in the art, a sucker rod pump includes at least two separate valves as well as other pump components such as a barrel, plunger, and anchor. Beginning at the south end, oil pumps generally include a standing valve, which has a ball therein, the purpose of which is to regulate the passage of oil (or other substance being pumped) from downhole into the pump, allowing the pumped matter to be moved northward out of the system and into the flow line, while preventing the pumped matter from dropping back southward into the hole. Oil is permitted to pass through the standing valve and into the pump by the movement of the ball off its seat, and oil is prevented from dropping back into the hole by the seating of the ball. North of the standing valve, coupled to the sucker rod, is a traveling valve. The purpose of the traveling valve is to regulate the passage of oil from within the pump northward in the direction of the flow line, while preventing the pumped oil from dropping back in the direction of the standing valve and hole.
Actual movement of the pumped substance through the system will now be discussed. Oil is pumped from a hole through a series of “downstrokes” and “upstrokes” of the oil pump, which motion is imparted by the above-ground pumping unit. During the upstroke, formation pressure causes the ball in the standing valve to move upward, allowing the oil to pass through the standing valve and into the barrel of the oil pump. This oil will be held in place between the standing valve and the traveling valve. In the traveling valve, the ball is located in the seated position, held there by the pressure from the oil that has been previously pumped.
On the downstroke, the ball in the traveling valve unseats, permitting the oil that has passed through the standing valve to pass therethrough. Also during the downstroke, the ball in the standing valve seats, preventing pumped oil from moving back down into the hole. The process repeats itself again and again, with oil essentially being moved in stages from the hole, to above the standing valve and in the oil pump, to above the traveling valve and out of the oil pump. As the oil pump fills, the oil passes through the pump and into the tubing. As the tubing is filled, the oil passes into the flow line, from which oil is taken to a storage tank or other such structure.
Presently known designs of sucker rod pumps suffer from several shortcomings in various areas of the design. The ball and seat components used in both the traveling valve and the standing valve are exposed to wear. The seat components are also subject to high pressures, particularly in deep wells, which can lead to cracking. Hence, it would be desired to develop sucker rod pumps having valves that display improved wear and cracking resistance.